In a standard evolution process of a wireless local access network (Wireless local access network, referred to as WLAN), an important characteristic is backward compatibility, that is, a new access point (Access Point, hereinafter referred to as AP) and a station (STA) may be transferred in an old format, the old STA may normally communicate under the new AP. In the WLAN standard evolution process of an orthogonal frequency division multiplexing (orthogonal frequency division multiplexing, hereinafter referred to as OFDM) system, the bandwidth gradually becomes large. A bandwidth of 20 MHz is adopted in the initial IEEE 802.11a, the bandwidth is extended to 40 MHz in IEEE 802.11n, the bandwidth is further extended to 80 MHz and 160 MHz (80+80 MHz) in IEEE 802.11ac, and a larger communication bandwidth may be adopted in the future WLAN standard. The network is upgraded to apply a new standard, and the original device is generally compatible in the upgrading process. When the network is upgraded, for example, upgraded from an IEEE 802.11n network to an IEEE 802.11ac network, two new and old stations will exist, the old station is a legacy STA, and is a station before the network is upgraded and supports the standard before upgrade, for example, standard IEEE 802.11n, the new station is a newly added station, is a station deployed after the network is upgraded and supports two standards before and after upgrade, for example, both supporting IEEE 802.11n and IEEE 802.11ac.
However, no matter how large the total communication bandwidth is extended, a primary channel and a secondary channel beyond the primary channel exist. In a communication process, both the new station and the old station must select a channel including the primary channel to transmit data. Since the bandwidth capable of being supported by the legacy STA is relatively small, while the bandwidth capable of being supported by the new station is relatively large, when the old station sends data to the AP, the bandwidth resources will be wasted seriously.